I was able to get my old Athlon XP 1700+ working recently (with a really horrid motherboard... 2 PCI slots, no AGP), so I put it in it's old case, and pulled out a 128 and 256 stick of ram from my computer to go in there, along with a 40gig HDD and 56X CD-Rom. Then an old Voodoo 3 I found. All in all, a pretty nice system! XD

Anyways, it seems that it has a few problems. I cannot run it in 133/133 frequency (Used to be able to), so I have to run it in 100/100. Also, it seems that it will not stay on for more than 8-10 hours (then it shuts down).

Could this be a problem with the powersupply? Or could it be something else?

I would think a 300W power supply would be OK ... how about the heatsink/fan for the processsor?----------------------------------Here is a 300 W power supply case for a AMD processor ... so it should be OK:

I checked and they recommend that case for many Athlon 1800XP+ so 300W power should be OK ...

It could be a bad power supply....--------------------------------I would flash the BIOS to the latest from the manufacturer, and make sure that the Power Saving stuff (suspend to disk, etc.) is turned off in the bios...and make sure the processor heatsink is installed well and the heatsink fan is properly functioning.

just one more storie, once I had a Nforce2 chipset with a XP1700+ proc 256DDR ram...everything worked fine, network was fast...and one day things started happening the machine was getting slower when doing things, it hanged randomly I switched everything in it...except the network card and nothing...then after I've almost gave up I've put in another network card and the system was rock solid...you know what happened to that network card? , I few grenades...and a couple of rounds from my UZI took care of it... [nah okay , I was only using the axe to finish the job ]